The present invention relates generally to memory devices and more particularly, the present invention relates to decoding and counting of memory addresses in such devices.
The performance of computer systems has improved dramatically due to a rapid growth in computer architecture design and particularly in the performance of computer memory. However, access times to the data residing in computer memory has not improved at a corresponding rate.
FIG. 1 is a typical memory device. In particular, FIG. 1 illustrates memory device 100 that includes control 38, latch 18, row decode 22, counter 26, column decode 30, memory array 12, input/output (I/O) logic and latches 34 and write drivers and data sense amplifiers 52. Memory device 100 can be coupled to an external microprocessor or memory controller for memory accessing and is used to store data which is accessed via data bus 10. It will be appreciated by those skilled in the art that additional circuitry and control signals can be provided.
For example, for a write operation, an address along with data is inputted to memory device 100 through address bus 16 and data bus 10, respectively. The data on data bus 10 is written into memory array 12 at the address given by address bus 16. In particular, row address strobe (/RAS) signal 14, column address strobe (/CAS) signal 24, write enable (/WE) signal 36 and output enable (/OE) signal 42, which are coupled to control 38, latch 18, counter 26 and 1/0 logic and latches 34, control the input and output to and from memory array 12, as is known in the art. Based on these control signals, the address is decoded by row decode 22 and column decode 30 through latch 18 and counter 26, respectively, thereby activating the memory cells that are being written to using write drivers and data sense amplifiers 52, as is known in the art. The data on data bus 10 is then written to these activated memory cells of memory array 12 through I/O bus 32.
Disadvantageously, due to the low latency (i.e., zero clocks) of the write path and the setup requirements of writing to memory array 12, the logic that decodes the column address (i.e., column decode 30) used for enabling the proper write drivers can be in the critical path of memory device 100.
Moreover, for embodiments of memory device 100 that includes compare circuitry to determine whether a page count is complete during a read or write operation, conventional circuitry compares a decoded version of the memory address to a reference version of such a memory address that is also decoded. Disadvantageously, this decode-to-decode compare circuitry requires many gates to perform the compare, thereby decreasing the speed of such a compare and also increasing the size of memory devices using such circuitry. Accordingly, there is a need for a reduction of the criticality of the decode logic path of such memory devices. as well as a faster and smaller compare circuitry to determine whether a page count is complete during read and write operations of such devices. For these and other reasons there is a need for the present invention.
The above-mentioned problems with access times of memory devices and other problems are addressed by the present invention and will be understood by reading and studying the following specification. Structures and methods are described which accord improved benefits for accessing of memory devices.
In particular, improved methods and structures are provided that reduce the criticality of a decode logic path for a memory device by moving the decode logic circuitry prior to the counter circuitry for a memory device, thereby enabling the decoding of the write drivers and data sense amplifiers during the setup time of a load path of the memory device. Further, improved methods and structures are provided that enable the determination of when a page count is complete in a memory array of a memory device with smaller and faster circuitry than current conventional count complete circuitry.
Embodiments of a structure include a memory device that comprises a decode logic circuitry that decodes an address. The memory device also includes a counter circuitry coupled to the decode logic circuitry that generates a counter value based on the decoded address. Embodiments of the present invention also includes methods, other structures as well as systems incorporating such structures all formed according to the methods provided in this application.
Additionally, other embodiments of a structure include a compare circuit that determines whether a page count is complete in a memory structure. The compare circuit includes a holding circuitry that includes a number of latches for holding an encoded version of a memory address. The compare circuit also includes a multiplexing circuitry coupled to the holding circuitry. The multiplexing circuitry receives the encoded version of the memory address from the holding circuitry and a decoded version of the memory address from a decoder, such that the multiplexing circuitry uses the encoded version to select one bit of the decoded version of the memory address to determine whether the page count is complete for the memory structure.